Prostate cancer accounts for over 35% of all cancers among men in the United States. The long-term objective of our research is to identify innovative preventive strategies by applying the knowledge from preclinical efficacy studies to individuals at high risk for prostate cancer. Epidemiological studies suggest that regular use of non-steroidal antiinflammatory drugs (NSAIDs), including aspirin, might be as protective against prostate cancer as it is against colon cancer, although NSAIDs may have some side effects due to non-selectivity in inhibiting COX-1 and COX-2. NSAIDs induce beneficial effects primarily through the inhibition of cyclooxygenases. It is not clear however, whether selective COX-2 inhibitors, or exisulind, a metabolic product of sulindac (NSAID), exert their potentially beneficial effects either by blocking COX-2 or by stimulating programmed cell death via other pathways. The proposed studies will test the hypothesis that celecoxib and exisulind, administered in combination, increase the chemopreventive efficacy synergistically by blocking COX-2 and other proinflammatory genes and by stimulating programmed cell death. We will use a well-established rat model for dorsolateral prostate cancer, induced with methylnitrosourea (MNU)/testosterone, to test our hypothesis. The specific aims are (1) to determine the chemopreventive efficacy of celecoxib and exisulind, administered individually and in combination against MNU/testosterone-induced prostate cancer in rats, (2) to compare the differences in COX-2 expression in tumors derived from the dorsolateral prostate of rats treated with celecoxib and exisulind individually and in combination;and (3) to identify target genes and transcription factors associated with the cascade of events leading to tumor growth inhibition involved in COX-2- dependent and-independent pathways using DNA microarrays. Total RNA will be isolated from rat prostate tumors, and the cDNA will be hybridized with rat DNA microarrays. The expressed genes will be confirmed with RT-PCR, and Western Blot analyses. Part of the research strategy in this study is to elucidate the functional mechanisms of celecoxib and exisulind that are operating via COX-2 -dependent and -independent mechanisms in prostate cancer prevention. A high throughput analysis using rat cDNA microarray technology will help us to identify the signature genes of these agents and their mechanistic pathways in prostate tumor growth inhibition. Clear delineation of the chemopreventive efficacy of celecoxib and exisulind in this preclinical model of prostate cancer will allow the rational design of human clinical trials.